The present invention relates, in general, to semiconductor devices, and more particularly, to semiconductor devices that have non-linear parasitic affects.
FIG. 1 is a graph 10 illustrating the performance of a conventional body-tied, partially depleted field effect transistor (FET) that is formed in a silicon-on-insulator (SOI) substrate. A line 11 is used to represent the amount of current in amps (A), indicated by a y-axis 14, that the FET produces as the voltage potential on the gate of the FET (V.sub.g) is varied. The voltage potential is indicated in graph 10 along an x-axis 15 in volts.
One problem that is common to conventional body-tied FETs formed in SOI substrates is the presence of a "kink" region in the output performance of the FET. This "kink" region is indicated in graph 10 with a bracket 13. The "kink" region occurs as a FET device transitions from a non-conductive state to a conductive state during operation. This transition is also indicated in graph 10 by a bracket 12.
Up to now, the exact cause of the "kink" problem in body-tied FETs formed in SOI substrates has not been identified. However, the impact of "kink" affect on the performance of FETs formed in SOI substrates is significant. The "kink" problem reduces the breakdown voltage, creates anomalous subthreshold characteristics, affects the linearity of the device, and results in high leakage current and increased power consumption.
Accordingly, a need exists to first identify the cause of the "kink" problem associated with conventional body-tied FETs formed in SOI substrates and then to provide a FET in an SOI substrate that does not suffer from the "kink" effect problem.